The Big Thompson Flood

On the evening of July thirty-first, nineteen seventy-six, Colorado was hours away from celebrating its hundredth birthday as a state. An estimated two thousand five hundred to three thousand five hundred people were in Big Thompson Canyon along US Route Thirty-Four, one of Colorado's most popular summer corridors, connecting Estes Park to the plains at Loveland. Many had driven up specifically for the centennial weekend.

A thunderstorm stalled over the headwaters of the Big Thompson River above the canyon. It did not move. Over the course of the evening it dropped between twelve and fourteen inches of rain onto a narrow drainage basin. In a single hour, seven and a half inches fell. The canyon, cut through granite, offered the water nowhere to go but down.

The Big Thompson River rose thirty-eight times its normal flow within hours. A wall of water, estimated at twenty feet high in some stretches, rushed down a canyon that is in places barely wide enough for the two-lane road and the river together. The water carried boulders, cars, sections of highway, and everything built along the banks.

One hundred forty-four people died. Five were never found. The flood destroyed four hundred eighteen homes, fifty-two businesses, every bridge in the canyon, and miles of paved road. The damage in nineteen seventy-six dollars totaled nearly forty million.

A highway patrol officer, Sergeant Hugh Purdy, drove into the canyon and used his loudspeaker to warn people to leave their cars and climb the canyon walls. He was swept away and killed while doing so. His last radio transmission told dispatch that the water was rising too fast.

The Colorado State Patrol set a new rule after the flood: when a flash flood threatens a canyon with no exit, the command is to abandon the vehicle and climb to high ground immediately. Signs now posted along this stretch of US Thirty-Four carry that instruction. The flood remains the deadliest flash flood in Colorado recorded history.